Use GitHub releases to download python versions (#85)

This pull-request improves `setup-python` action to add ability to download specific version of Python on flight if it is not available by default.

**Details:**
`setup-python` action will download and install specific Python version from GitHub releases ([actions/python-versions](https://github.com/actions/python-versions/releases)) in case the version is not found in the local cache. All versions of Python available for installation are published in [actions/python-versions](https://github.com/actions/python-versions) repository.
All available versions are listed in the [version-manifest.json](https://github.com/actions/python-versions/blob/master/versions-manifest.json) file.

**Installation time:**

- Ubuntu / macOS: 10-20 seconds
- Windows: ~ 1 minute (mostly related to fact that we use MSI installer for Python on Windows)

Co-authored-by: MaksimZhukov <v-mazhuk@microsoft.com>
Co-authored-by: Konrad Pabjan <konradpabjan@github.com>
Co-authored-by: Brian Cristante <33549821+brcrista@users.noreply.github.com>

action.yml

@@ -8,7 +8,9 @@ inputs:
     default: '3.x'
   architecture:
     description: 'The target architecture (x86, x64) of the Python interpreter.'
-    default: 'x64'
+  token:
+    description: Used to pull python distributions from actions/python-versions. Since there's a default, this is typically not supplied by the user.
+    default: ${{ github.token }}
 outputs:
   python-version:
     description: "The installed python version. Useful when given a version range as input."